22 cards where the set is “war” and the text includes “amass”

Angrath, Captain of Chaos (War of the Spark #227)
Aven Eternal (War of the Spark #42)
Bleeding Edge (War of the Spark #78)
Callous Dismissal (War of the Spark #44)
Commence the Endgame (War of the Spark #45)
Crush Dissent (War of the Spark #47)
Dreadhorde Invasion (War of the Spark #86)
Dreadhorde Twins (War of the Spark #126)
Enter the God-Eternals (War of the Spark #196)
Eternal Skylord (War of the Spark #49)
Gleaming Overseer (War of the Spark #198)
Grim Initiate (War of the Spark #130)
Herald of the Dreadhorde (War of the Spark #93)
Honor the God-Pharaoh (War of the Spark #132)
Invade the City (War of the Spark #201)
Invading Manticore (War of the Spark #134)
Lazotep Plating (War of the Spark #59)
Lazotep Reaver (War of the Spark #96)
Relentless Advance (War of the Spark #64)
Toll of the Invasion (War of the Spark #108)
Vizier of the Scorpion (War of the Spark #111)
Widespread Brutality (War of the Spark #226)

This search is finished. Now the real work can begin.